Electrically heated thermal latch



y 1934- N. H. KIMBALL ELECTRICALLY HEATED THERMAL LATCH Filed July 25.1953 Patented May 1, 1934 UNITED STATES PATENT OFFICE 2 Claim.

This invention relates to an electrically heated thermal latch or safetydevice.

One of its objects is to provide a safety device to be placed between acontrol motor and a fuel 5 valve and connected thereto, for use on gasor oil burning furnaces.

Another object of this invention is to provide an electrically heatedthermal latch or safety device that will automatically disconnect thevalve control motor from the valve controlling the flow of fuel to thefurnace if electric current to the control motor is broken in anymanner.

It is customary with gas or oil burning furnaces to have a thermostaticcontrol apparatus to control the heat of the furnace to control theopening and closing of a fuel supply valve. If the electric current isbroken to the apparatus in any manner it stops working. If it shouldstop when p the valve was open, the valve would remain open as it isconnected to the control motor this would allow fuel to flow into thefurnace with serious results. There have been cases where this hasoccurred where the boiler and furnace were completely ruined and sometimes the building set afire as well.

With my invention attached to the control motor and fuel supply valvethe above would never have happened for as soon as the electric currentwas broken the yoke would begin to cool and move away from the latch barwhich will allow the latch bar to move away from its catch and fall toits lowest position, thus the control motor and fuel valve aredisconnected which allows the valve to close and stops the flow of fuelto the furnace.

As soon as the pull is removed from the valve it closes in its usualmanner.

With these and other objects in view my invention consists of thefollowing construction of its parts to be hereinafter described andclaimed.

In the accompanying drawing forming a part of this specification and inwhich corresponding parts are denoted by like reference characters isillustrated the preferred form of embodiment of the invention capable ofcarrying the same into practical use, it being understood that theinvention is not necessarily limited thereto, as various changes in itsshape and proportions and general assemblage of its parts may beresorted to without departing from the principles of the invention, andthe right is therefor reserved to make all changes and modificationswhich will fall within the scope of the invention.

Referring to the drawing:

- Figure 1 is a view showing a part of a controlling apparatus of afurnace with my invention attached thereto.

Fig. 2 is a side view of the latch bar 1.

Fig. 3 is a fragmentary section view showing the latch bar in its lowestposition.

Fig. 4 is a vertical section view showing the latch bar in its upperdisconnected position.

Fig. 5 is a vertical section view showing the latch bar in its lockedposition.

The reference character A denoted the casing 5 for an electric switch, Ba control motor, C the casing for the fuel supply valve, D my invention,

E a transformer for transforming the electric current to the heatingunit.

The invention comprises a casing having a thread on each end thereof.The upper end has a cap 3 threaded thereon having an eye thereon towhich is secured one end of a chain 5 the other end of the chain beingattached to the crank of the control motor B.

Threaded onto the lower end of the casing is another cap '7 which has anaperture therein into which is threaded one end of a pipe 8 the otherend of the pipe projecting into the casing.

Into the lower end of the pipe 8 is threaded a plug 9 which has anaperture therein, through which passes a latch bar 1. A pin passingthrough the latch bar forms lugs 11 which prevent the latch falling outof the casing when it is in its lower position.

The reference numeral 12 denotes an expansible yoke which is secured byone end to the upper end of the pipe 8 by rivets 18 or other means.Secured to the yoke 12 is a heating unit 13 which is controlled by anelectric current passing through cable 22 from the transformer to theheating unit. When the electric current is passing through the heatingunit it heats the yoke to expand it to move the latch bar to its lockedposition as shown in Fig. 5.

Placed within the pipe 8 near the upper end is a lug 14 over which thenotch 15 in the latch bar engages when the latch bar is moved by theyoke 12 into its locked position.

The upper end of the latch bar has a projection thereon to which thefree end of the yoke engages when said casing is lowered relative tosaid bar.

One end of a chain 19 is secured to the lower end of the latch bar 1 theother end of the chain being secured to the valve lever 20. The opening2 of the control valve is controlled by the movement of the lever 20,thus when the control motor and the valve lever is connected by means of110 my invention and the control motor is operated it will raise andlower the valve.

Having thus described my invention what I claim as new and desire tosecure by Letters Patent, is:

1. An electrically heated thermal latch comprising a casing having endsthereto, one of said ends having an eye thereon, the other end having anaperture therein, a pipe threaded into said aperture and extending intosaid casing, an expansible yoke having one end secured to the upper endof said pipe within said casing, a latch bar within said pipe and havinga notch therein, said casing and bar being relatively movable, said pipehaving a lug therein which notched latch bar may engage, said latch barcontracting the free end of said yoke when said casing is loweredrelative to said bar, a heating unit secured to said yoke which whenheated causes said yoke to move said latch bar to latch with said lug,means for supplying an electric current to said heating unit and meansfor preventing said latch bar from falling out of said casing.

2. An electrically heated thermal latch comprising a casing having endsthereto, one of said ends having an eye thereon to which a chain isattached to support said casing, the other end of said casing having anaperture therein, a pipe threaded into said aperture and extending intosaid casing, an expansible yoke having one end secured to the inner endof said pipe, a heating unit secured to said yoke, means for supplyingan electric current to said heating unit, said pipe has a plug in thelower end thereof having an aperture therein, a latch bar passingthrough said aperture into said casing, said latch bar contracting thefree end of said yoke when said casing is lowered relative to said bar,said heating unit when heated causes said yoke to move said latch bar tolatch with a lug within said pipe and means to prevent said latch barfalling out of said casing.

NORMAN H. KIMBALL,

